• Anthocyanins
• Carotenoids
• Chlorophylls
• Genes.
• Light
• Pigments

This study investigates the role of the transcription factor SlBBX24 in tomato morphogenesis and anthocyanin biosynthesis. Using T1 plants of tomato independent lines overexpressing SlBBX24 gene, the study examines transgene expression levels and relative impacts on plant phenotype, including flowering and fruiting time, and secondary metabolites’ production, such as chlorophylls, carotenoids, and anthocyanins. The overexpression of SlBBX24 affects key plant processes such as light-mediated signaling and morphogenesis, and anthocyanin and flavonoid metabolic pathways, potentially interacting with other molecules. Notably, the transgenic line characterized by the highest transgene expression exhibited increased anthocyanin production in vegetative tissues (but not in fruits), reduced leaf chlorophyll content, and prolonged vegetative phase, with relative delays in flowering time and fruit setting. These findings suggest that SlBBX24 is involved in light signaling processes which also activate the flavonoid pathway, particularly the anthocyanin branch. This contrasts with findings in Arabidopsis thaliana, where the ortholog AtBBX24 factor inhibits anthocyanin biosynthesis. Further research is needed to understand this discrepancy and to characterize SlBBX24 role in tomato secondary compound biosynthesis and stress responses.